fixes from Tim Elliott

ChangeLog

@@ -3,6 +3,9 @@
   necessary
 - oops vipsthumbnail sharpening was turning off for integer shrinks, 
   thanks Nicolas
+- im_vips2jpeg() could fail for very small images (thanks Tim)
+- threadpool wasn't stopping on allocate errors (thanks Tim)
+- vips_sink_disc() could block if allocate failed (thanks Tim)
 
 12/5/10 started 7.22.1
 - fix a problem with tiff pyramid write and >1cpu, thanks Ruven

libvips/format/im_vips2jpeg.c

@@ -31,6 +31,10 @@
  * 	- allow "none" for profile, meaning don't embed one
  * 4/2/10
  * 	- gtkdoc
+ * 17/7/10
+ * 	- use g_assert()
+ * 	- allow space for the header in init_destination(), helps writing very
+ * 	  small JPEGs (thanks Tim Elliott)
  */
 
 /*
@@ -106,7 +110,6 @@ im_vips2mimejpeg( IMAGE *in, int qfac )
 #include <stdlib.h>
 #include <string.h>
 #include <setjmp.h>
-#include <assert.h>
 
 #ifdef HAVE_EXIF
 #ifdef UNTAGGED_EXIF
@@ -442,7 +445,7 @@ write_profile_data (j_compress_ptr cinfo,
   unsigned int length;          /* number of bytes to write in this marker */
 
   /* rounding up will fail for length == 0 */
-  assert( icc_data_len > 0 );
+  g_assert( icc_data_len > 0 );
 
   /* Calculate the number of markers we'll need, rounding up of course */
   num_markers = (icc_data_len + MAX_DATA_BYTES_IN_MARKER - 1) / 
@@ -563,9 +566,9 @@ write_vips( Write *write, int qfac, const char *profile )
 
 	/* Should have been converted for save.
 	 */
-        assert( in->BandFmt == IM_BANDFMT_UCHAR );
-	assert( in->Coding == IM_CODING_NONE );
-        assert( in->Bands == 1 || in->Bands == 3 || in->Bands == 4 );
+        g_assert( in->BandFmt == IM_BANDFMT_UCHAR );
+	g_assert( in->Coding == IM_CODING_NONE );
+        g_assert( in->Bands == 1 || in->Bands == 3 || in->Bands == 4 );
 
         /* Check input image.
          */
@@ -794,8 +797,14 @@ METHODDEF(void)
 init_destination( j_compress_ptr cinfo )
 {
 	OutputBuffer *buf = (OutputBuffer *) cinfo->dest;
-	int mx = cinfo->image_width * cinfo->image_height * 
-		cinfo->input_components * sizeof( JOCTET );
+
+	/* Allocate an extra 1,000 bytes for header overhead on small images.
+	 *
+	 * TODO: use empty_output_buffer() instead in order to accomodate 
+	 * headers larger than 1,000 bytes.
+	 */
+ 	int mx = cinfo->image_width * cinfo->image_height * 
+		cinfo->input_components * sizeof( JOCTET ) + 1000;
 
 	/* Allocate relative to the image we are writing .. freed when we junk
 	 * this output.

libvips/iofuncs/sinkdisc.c

@@ -5,6 +5,8 @@
  * 	- move on top of VipsThreadpool, instead of im_threadgroup_t
  * 23/6/10
  * 	- better buffer handling for single-line images
+ * 17/7/10
+ * 	- we could get stuck if allocate failed (thanks Tim)
  */
 
 /*
@@ -529,8 +531,13 @@ vips_sink_disc( VipsImage *im, VipsRegionWrite write_fn, void *a )
 	 * We can't just free the buffers (which will wait for the bg threads 
 	 * to finish), since the bg thread might see the kill before it gets a 
 	 * chance to write.
+	 *
+	 * If the pool exited with an error, write.buf might not have been
+	 * started (if the allocate failed), and in any case, we don't care if
+	 * the final write went through or not.
 	 */
-	im_semaphore_down( &write.buf->done );
+	if( !result )
+		im_semaphore_down( &write.buf->done );
 
 	im__end_eval( im );
 

libvips/iofuncs/threadpool.c

@@ -10,6 +10,9 @@
  * 11/5/10
  * 	- argh, stopping many threads could sometimes leave allocated work
  * 	  undone
+ * 17/7/10
+ * 	- set pool->error whenever we set thr->error, lets us catch allocate
+ * 	  errors (thanks Tim)
  */
 
 /*
@@ -348,7 +351,7 @@ typedef struct _VipsThreadpool {
 	/*< private >*/
 	VipsImage *im;		/* Image we are calculating */
 
-	/* STart a thread, do a unit of work (runs in parallel) and allocate 
+	/* Start a thread, do a unit of work (runs in parallel) and allocate 
 	 * a unit of work (serial). Plus the mutex we use to serialize work 
 	 * allocation.
 	 */
@@ -507,6 +510,7 @@ vips_thread_work_unit( VipsThread *thr )
 
 	if( vips_thread_allocate( thr ) ) {
 		thr->error = TRUE;
+		pool->error = TRUE;
 		g_mutex_unlock( pool->allocate_lock );
 		return;
 	}
@@ -522,8 +526,10 @@ vips_thread_work_unit( VipsThread *thr )
 
 	/* Process a work unit.
 	 */
-	if( vips_thread_work( thr ) )
+	if( vips_thread_work( thr ) ) {
 		thr->error = TRUE;
+		pool->error = TRUE;
+	}
 }
 
 #ifdef HAVE_THREADS